Juan Manuel Pastor

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We propose a new nestedness estimator that takes into account the weight of the interactions, that is, it runs over frequency matrices. A nestedness measurement is calculated through the average distance from each matrix cell containing a link to the cell with the lowest marginal totals, in the packed matrix, using a weighted Manhattan distance. The(More)
Several ecosystem services directly depend on mutualistic interactions. In species rich communities, these interactions can be studied using network theory. Current knowledge of mutualistic networks is based mainly on binary links; however, little is known about the role played by the weights of the interactions between species. What new information can be(More)
Mutualistic communities have an internal structure that makes them resilient to external perturbations. Late research has focused on their stability and the topology of the relations between the different organisms to explain the reasons of the system robustness. Much less attention has been invested in analyzing the systems dynamics. The main population(More)
Complex networks are a recent type of framework used to study complex systems with many interacting elements, such as self-organized criticality (SOC). The network nodes' tendency to link to other nodes of similar type is characterized by assortative mixing. Real networks exhibit assortative mixing by vertex degree, however, typical random network models,(More)
High robustness of complex ecological systems in the face of species extinction has been hypothesized based on the redundancy in species. We explored how differences in network topology may affect robustness. Ecological bipartite networks used to be small, asymmetric and sparse matrices. We created synthetic networks to study the influence of the properties(More)
Manuel Jiménez-Mart́ın, Juan Carlos Losada, Juan Manuel Pastor, and Javier Galeano Departamento de F́ısica Fundamental, Despacho 2.27, Facultad de Ciencias, Universidad Nacional de Educación a Distancia (UNED), Paseo Senda del Rey 9, E-28040, Madrid, Spain. +34 91 3987636. Grupo de Sistemas Complejos, Dept. Ciencia y Tecnoloǵıa aplicadas a la I.T. Agŕıcola,(More)
Dynamic population models are based on the Verhulst’s equation (logisitic equation), where the classic Malthusian growth rate is damped by intraspecific competition terms. Mainstream population models for mutualism are modifications of the logistic equation with additional terms to account for the benefits produced by the interspecies interactions. These(More)
BACKGROUND Network analysis has become a relevant approach to analyze cascading species extinctions resulting from perturbations on mutualistic interactions as a result of environmental change. In this context, it is essential to be able to point out key species, whose stability would prevent cascading extinctions, and the consequent loss of ecosystem(More)
Degree ssortativity is the tendency for nodes of high degree (resp. low degree) in a graph to be connected to high degree nodes (resp. to low degree ones). It is usually quantified by the Pearson correlation coefficient of the degree-degree correlation. Here we extend this concept to account for the effect of second neighbours to a given node in a graph.(More)
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